Effects of Varying Proportions of Glass on Reflectance Spectra of HED Polymict Breccias

Some meteorites contain significant amounts of glass, which, in most cases, probably results from impact processes on parent bodies.. Yamato 82202 is an example of one of the unequilibrated eucrites that contains significant proportions of impact glass distributed as veins throughout the meteorite. In other cases, fragments of glass are distributed throughout polymict breccias. For example, the polymict eucrite EET 87509 contains rare angular fragments of devitrified glass. Proportions of glass in most of these meteorites and in lithic clasts within these meteorites may vary locally from small amounts (less than one percent) to much larger amounts (subequal proportions of glass and mineral material). For example, some fragments within the South African polymict eucrite Macibini contain approximately 50% glass. The presence of these variable proportions of meteorite glass confirm the increased recognition that impact processes played an important role in the histories of asteroidal bodies. This study attempts to quantify the effects of a glass component on reflectance spectra by analyzing in the laboratory mixtures of varying proportions of a well-characterized HED polymict breccia and glass derived by melting a bulk sample of that breccia

A specific group of genes respond to cold dehydration stress in cut Alstroemeria flowers whereas ambient dehydration stress accelerates developmental senescence expression patterns

Petal development and senescence entails a normally irreversible process. It starts with petal expansion and pigment production, and ends with nutrient remobilization and ultimately cell death. In many species this is accompanied by petal abscission. Post-harvest stress is an important factor in limiting petal longevity in cut flowers and accelerates some of the processes of senescence such as petal wilting and abscission. However, some of the effects of moderate stress in young flowers are reversible with appropriate treatments. Transcriptomic studies have shown that distinct gene sets are expressed during petal development and senescence. Despite this, the overlap in gene expression between developmental and stress-induced senescence in petals has not been fully investigated in any species. Here a custom-made cDNA microarray from Alstroemeria petals was used to investigate the overlap in gene expression between developmental changes (bud to first sign of senescence) and typical post-harvest stress treatments. Young flowers were stressed by cold or ambient temperatures without water followed by a recovery and rehydration period. Stressed flowers were still at the bud stage after stress treatments. Microarray analysis showed that ambient dehydration stress accelerates many of the changes in gene expression patterns that would normally occur during developmental senescence. However, a higher proportion of gene expression changes in response to cold stress were specific to this stimulus and not senescence related. The expression of 21 transcription factors was characterized, showing that overlapping sets of regulatory genes are activated during developmental senescence and by different stresses

Delivery of Dark Material to Vesta via Carbonaceous Chondritic Impacts

NASA's Dawn spacecraft observations of asteroid (4) Vesta reveal a surface with the highest albedo and color variation of any asteroid we have observed so far. Terrains rich in low albedo dark material (DM) have been identified using Dawn Framing Camera (FC) 0.75 {\mu}m filter images in several geologic settings: associated with impact craters (in the ejecta blanket material and/or on the crater walls and rims); as flow-like deposits or rays commonly associated with topographic highs; and as dark spots (likely secondary impacts) nearby impact craters. This DM could be a relic of ancient volcanic activity or exogenic in origin. We report that the majority of the spectra of DM are similar to carbonaceous chondrite meteorites mixed with materials indigenous to Vesta. Using high-resolution seven color images we compared DM color properties (albedo, band depth) with laboratory measurements of possible analog materials. Band depth and albedo of DM are identical to those of carbonaceous chondrite xenolith-rich howardite Mt. Pratt (PRA) 04401. Laboratory mixtures of Murchison CM2 carbonaceous chondrite and basaltic eucrite Millbillillie also show band depth and albedo affinity to DM. Modeling of carbonaceous chondrite abundance in DM (1-6 vol%) is consistent with howardite meteorites. We find no evidence for large-scale volcanism (exposed dikes/pyroclastic falls) as the source of DM. Our modeling efforts using impact crater scaling laws and numerical models of ejecta reaccretion suggest the delivery and emplacement of this DM on Vesta during the formation of the ~400 km Veneneia basin by a low-velocity (<2 km/sec) carbonaceous impactor. This discovery is important because it strengthens the long-held idea that primitive bodies are the source of carbon and probably volatiles in the early Solar System.Comment: Icarus (Accepted) Pages: 58 Figures: 15 Tables:

Can musical training influence brain connectivity?:Evidence from diffusion tensor MRI

In recent years, musicians have been increasingly recruited to investigate grey and white matter neuroplasticity induced by skill acquisition. The development of Diffusion Tensor Magnetic Resonance Imaging (DT-MRI) has allowed more detailed investigation of white matter connections within the brain, addressing questions about the effect of musical training on connectivity between specific brain regions. Here, current DT-MRI analysis techniques are discussed and the available evidence from DT-MRI studies into differences in white matter architecture between musicians and non-musicians is reviewed. Collectively, the existing literature tends to support the hypothesis that musical training can induce changes in cross-hemispheric connections, with significant differences frequently reported in various regions of the corpus callosum of musicians compared with non-musicians. However, differences found in intra-hemispheric fibres have not always been replicated, while findings regarding the internal capsule and corticospinal tracts appear to be contradictory. There is also recent evidence to suggest that variances in white matter structure in non-musicians may correlate with their ability to learn musical skills, offering an alternative explanation for the structural differences observed between musicians and non-musicians. Considering the inconsistencies in the current literature, possible reasons for conflicting results are offered, along with suggestions for future research in this area

The Physical Properties of the Red Supergiant WOH G64: The Largest Star Known?

WOH G64 is an unusual red supergiant (RSG) in the Large Magellanic Cloud (LMC), with a number of properties that set it apart from the rest of the LMC RSG population, including a thick circumstellar dust torus, an unusually late spectral type, maser activity, and nebular emission lines. Its reported physical properties are also extreme, including the largest radius for any star known and an effective temperature that is much cooler than other RSGs in the LMC, both of which are at variance with stellar evolutionary theory. We fit moderate-resolution optical spectrophotometry of WOH G64 with the MARCS stellar atmosphere models, determining an effective temperature of 3400 +/- 25 K. We obtain a similar result from the star's broadband V - K colors. With this effective temperature, and taking into account the flux contribution from the aysmmetric circumstellar dust envelope, we calculate log(L/L_sun) = 5.45 +/- 0.05 for WOH G64, quite similar to the luminosity reported by Ohnaka and collaborators based on their radiative transfer modeling of the star's dust torus. We determine a radius of R/R_sun = 1540, bringing the size of WOH G64 and its position on the H-R diagram into agreement with the largest known Galactic RSGs, although it is still extreme for the LMC. In addition, we use the Ca II triplet absorption feature to determine a radial velocity of 294 +/- 2 km/s for the star; this is the same radial velocity as the rotating gas in the LMC's disk, which confirms its membership in the LMC and precludes it from being an unusual Galactic halo giant. Finally, we describe the star's unusual nebula emission spectrum; the gas is nitrogen-rich and shock-heated, and displays a radial velocity that is significantly more positive than the star itself by 50 km/s.Comment: 25 pages, 5 figures; accepted for publication in The Astronomical Journa

Tactical Voting in Plurality Elections

How often will elections end in landslides? What is the probability for a head-to-head race? Analyzing ballot results from several large countries rather anomalous and yet unexplained distributions have been observed. We identify tactical voting as the driving ingredient for the anomalies and introduce a model to study its effect on plurality elections, characterized by the relative strength of the feedback from polls and the pairwise interaction between individuals in the society. With this model it becomes possible to explain the polarization of votes between two candidates, understand the small margin of victories frequently observed for different elections, and analyze the polls' impact in American, Canadian, and Brazilian ballots. Moreover, the model reproduces, quantitatively, the distribution of votes obtained in the Brazilian mayor elections with two, three, and four candidates.Comment: 7 pages, 4 figure

Keck spectroscopy and Spitzer Space Telescope analysis of the outer disk of the Triangulum Spiral Galaxy M33

In an earlier study of the spiral galaxy M33, we photometrically identified arcs or outer spiral arms of intermediate age (0.6 Gyr - 2 Gyr) carbon stars precisely at the commencement of the HI-warp. Stars in the arcs were unresolved, but were likely thermally-pulsing asymptotic giant branch carbon stars. Here we present Keck I spectroscopy of seven intrinsically bright and red target stars in the outer, northern arc in M33. The target stars have estimated visual magnitudes as faint as V \sim 25 mag. Absorption bands of CN are seen in all seven spectra reported here, confirming their carbon star status. In addition, we present Keck II spectra of a small area 0.5 degree away from the centre of M33; the target stars there are also identified as carbon stars. We also study the non-stellar PAH dust morphology of M33 secured using IRAC on board the Spitzer Space Telescope. The Spitzer 8 micron image attests to a change of spiral phase at the start of the HI warp. The Keck spectra confirm that carbon stars may safely be identified on the basis of their red J-K_s colours in the outer, low metallicity disk of M33. We propose that the enhanced number of carbon stars in the outer arms are an indicator of recent star formation, fueled by gas accretion from the HI-warp reservoir.Comment: 9 pages, 5 figures, accepted in A&

Spitzer/IRS 5-35 um Low-Resolution Spectroscopy of the 12 um Seyfert Sample

We present low-resolution 5.5-35 um spectra for 103 galaxies from the 12 um Seyfert sample, a complete unbiased 12 um flux limited sample of local Seyfert galaxies selected from the IRAS Faint Source Catalog, obtained with the Infrared Spectrograph (IRS) on-board Spitzer Space Telescope. For 70 of the sources observed in the IRS mapping mode, uniformly extracted nuclear spectra are presented for the first time. We performed an analysis of the continuum emission, the strength of the Polycyclic Aromatic Hydrocarbon (PAH) and astronomical silicate features of the sources. We find that on average, the 15-30 um slope of the continuum is alpha_{15-30}=-0.85+-0.61 for Seyfert 1s and -1.53+-0.84 for Seyfert 2s, and there is substantial scatter in each type. Moreover, nearly 32% of Seyfert 1s, and 9% of Seyfert 2s, display a peak in the mid-infrared spectrum at 20 um, which is attributed to an additional hot dust component. The PAH equivalent width decreases with increasing dust temperature, asindicated by the global infrared color of the host galaxies. However, no statistical difference in PAH equivalent width is detected between the two Seyfert types, 1 and 2, of the same bolometric luminosity. The silicate features at 9.7 and 18um in Seyfert 1 galaxies are rather weak, while Seyfert 2s are more likely to display strong silicate absorption. Those Seyfert 2s with the highest silicate absorption also have high infrared luminosity and high absorption (hydrogen column density N_H>10^23 cm^-2 as measured from the X-rays. Finally, we propose a new method to estimate the AGN contribution to the integrated 12 um galaxy emission, by subtracting the "star formation" component in the Seyfert galaxies, making use of the tight correlation between PAH 11.2 um luminosity and 12 um luminosity for star forming galaxies.Comment: accepted for publication in Ap

You are what you eat? Vegetarianism, health and identity

This paper examines the views of ‘health vegetarians’ through a qualitative study of an online vegetarian message board. The researcher participated in discussions on the board, gathered responses to questions from 33 participants, and conducted follow-up e-mail interviews with 18 of these participants. Respondents were predominantly from the United States, Canada and the UK. Seventy per cent were female, and ages ranged from 14 to 53 years, with a median of 26 years. These data are interrogated within a theoretical framework that asks, ‘what can a vegetarian body do?’ and explores the physical, psychic, social and conceptual relations of participants. This provides insights into the identities of participants, and how diet and identity interact. It is concluded that vegetarianism is both a diet and a bodily practice with consequences for identity formation and stabilisation